Gel materials, medical articles, and methods

ABSTRACT

A gel material and medical articles including such material, wherein the transparent gel material includes a polymerized poly(alkylene oxide) macromonomer that, prior to polymerization, is free-radically polymerizable, multifunctional (preferably difunctional), and has an average molecular weight of at least about 2000.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/121,518, filed Apr. 12, 2002, now allowed.

BACKGROUND

The present invention is directed to gel materials and medical articlesincorporating such materials, particularly medical articles useful aswound dressings. More particularly this invention is directed to gelmaterials prepared from a multifunctional poly(alkylene oxide)macromonomer.

Historically, exudate from a wound has been treated by absorbing itusing a dressing containing an absorbent material. Typical suchdressings contain a padded absorbent material attached to an adhesivetape backing. The padded absorbent material is applied to the wound toabsorb the wound exudate. A difficulty with this type of dressing isthat the scab typically forms in and as part of the pad as the woundheals. Thus, when the dressing is removed, the scab is removed. Thisproblem has been addressed by providing a porous film between theabsorbent material and the wound to reduce the likelihood that a scabformed will become attached to the absorbent material

More recently the use of so-called “occlusive” dressings for pressuresores and ulcers has gained increasing acceptance. A number of wounddressings of this kind are commercially available. Most of theseproducts are formed from several layers, including at least an innerskin-contacting layer and an outer backing layer. The dressing isapplied as a cover for the sore or ulcer in a size providing a marginaround the wound area that adhesively seals to the skin. The inner layercontains water-absorptive materials, so that fluid from the wound isabsorbed into the layer, making it possible to keep the dressing inplace for at least several days. Such occlusive dressings tend topromote healing by maintaining the wound under moist conditions withoutforming a crust, and serving as a barrier against bacterial infection.Such dressings for “moist wound healing” are particularly useful fordermal burns, traumatic skin deficiencies, incised wounds, and the like.

A wound care product in current use utilizes a hydrocolloid absorbent.Such a material typically has poor transparency so the treatment statecannot be observed from the outside. Also, such a material can partiallylose its integrity after absorbing wound fluid. Flexibility ofhydrocolloid dressings can be poor, which makes it difficult to applythe dressing to a bend portion of a body, such as a joint, etc. Theportion of the absorbent in contact with the wound is converted to agel-like material, and, when the dressing is removed, a portion of thisabsorbent material can be left in the wound, and must be removed topermit examination and/or before applying another dressing.

There are known hydrophilic gel materials useful in medical applicationssuch as wound dressings, however, many of them do not have theappropriate balance of absorption and cohesive strength often needed.Thus, additional such materials are needed. Furthermore, it would bedesirable to provide an occlusive material that is also transparent andflexible for use in a medical article such as a wound dressing or woundpacking material.

SUMMARY OF THE INVENTION

This invention provides medical articles and polymeric gel materials foruse therein, which are preferably absorbent, and more preferablyabsorbent and transparent. By “gel” (or “polymer gel” or “polymeric gelmaterial” or “hydrophilic gel”) it is meant a gel material capable ofswelling on contact with (or water-based fluids such as body fluidsincluding blood, plasma, and intracellular fluid or fluids similar tobody fluids such as physiological saline), but does not dissolve in,water. The gels are substantially continuous, i.e., lacking a cellularor void structure (although minor defects such as entrapped air bubblesor fractures may be present) and thus generally in a solid or semi-solidform. The term “gel” is used regardless of the state of hydration.Preferably, the gel does not include water until it comes in contactwith a surface from which it absorbs water (e.g., a wound).Significantly, even without water (or other plasticizing agents)preferred embodiments of the gel material of the present invention areflexible.

By “absorbent” it is meant that the material is preferably capable ofabsorbing fluids, particularly body fluids and preferably moderate toheavy amounts of body fluids, while retaining its structural integrity(i.e., remaining sufficiently intact such that it can perform thefunction of acting as an absorbent moist wound healing dressing, forexample), and preferably its transparency. By “transparent” it is meantthat when the preferred material is applied to a patient (e.g., at awound site), the area underlying the dressing can be visualizedsufficiently to permit observation of the wound by a health care worker.

The application of water swelling polymer gels to medical practice is,for example, found in wound dressings, wound packings, adhesives(particularly pressure sensitive adhesives), contact lenses, intraocularlenses, adhesives for biological tissues, adhesion preventing materials,adsorbents for blood purification, base materials for releasingpharmacologic agents, and the like. Materials for dental moldings orimpressions are another potential medical article use. Thus, as usedherein, “medical” applications encompasses dental applications,including dental adhesives, restoratives, coatings, composites,sealants, etc. Because water swelling polymer gels have compositions andmechanical properties similar to those of biological tissues, such gelsmay be applied in a wide variety of fields in the future.

In one embodiment, the present invention provides a medical article thatincludes a gel material including a homopolymer or copolymer of amultifunctional poly(alkylene oxide) free-radically polymerizablemacromonomer having a weight average molecular weight of at least about2000, wherein the multifunctional poly(alkylene oxide) macromonomercomprises a copolymeric random alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1; and R¹ is a (C1-C4)alkyl group. In this representation, there is arelatively random structural distribution of —CH(R¹)—CH₂—O— moieties and—CH₂—CH₂—O— moieties.

The present invention also provides a preferred embodiment of a medicalarticle, preferably a wound dressing, that includes a facing layer(preferably, a fluid permeable facing layer) and a backing layer(preferably, a moisture vapor permeable backing layer) with the gelmaterial (typically in the form of a layer) disposed between the two.Preferably the backing layer is both moisture vapor permeable and liquidimpermeable. The medical article, e.g., wound dressing, may furtherinclude a layer of pressure sensitive adhesive to secure the article tothe skin.

As used herein the terms “front surface” and “back surface” used withrespect to the gel layer, the facing layer, and the backing layer, referto the major surface of the indicated layer that, in use, faces towardthe wound surface or away from the wound surface, respectively.

That is, the gel material of the present invention, which is preferablyabsorbent and transparent, includes a polymerized poly(alkylene oxide)macromonomer that, prior to polymerization, is free-radicallypolymerizable, multifunctional (preferably difunctional), and has anaverage molecular weight of at least about 2000 (preferably at leastabout 4000, and more preferably at least about 6000). This gel materialcan be a homopolymer of the multifunctional macromonomer, or it can be acopolymer (i.e., having two or more different monomers), wherein atleast one of the monomers is a multifunctional macromonomer of the aboveformula. Other monomers that can be copolymerized with themultifunctional macromonomer include, for example, monofunctionalpoly(alkylene oxide) monomers, polar monomers, and hydrophobic monomers.

In one preferred embodiment, the present invention provides a medicalarticle that includes a gel material, which is preferably absorbent, andmore preferably absorbent and transparent. The gel material includes acopolymer prepared from monomers including: a multifunctionalpoly(alkylene oxide) free-radically polymerizable macromonomer having aweight average molecular weight of at least about 2000, wherein themultifunctional poly(alkylene oxide) macromonomer comprises acopolymeric alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1; and R¹ is a (C1-C4)alkyl group; a monofunctional poly(alkyleneoxide) monomer; and a polar monomer. As used herein, “a” or “an” mean“at least one” or “one or more” unless specifically indicated otherwise.

In one preferred embodiment, the present invention provides a medicalarticle that includes a gel material, which is preferably absorbent, andmore preferably absorbent and transparent. The gel material includes ahomopolymer or copolymer prepared from monomers including: about 5 wt-%to 100 wt-% of a multifunctional poly(alkylene oxide) free-radicallypolymerizable macromonomer having a weight average molecular weight ofat least about 2000, wherein the multifunctional poly(alkylene oxide)macromonomer comprises a copolymeric alkylene oxide moiety of theformula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1; and R¹ is a (C1-C4)alkyl group; 0 wt-% to about 80 wt-% of amonofunctional poly(alkylene oxide) monomer; and 0 wt-% to about 40 wt-%of a polar monomer.

Polymers of the present invention are prepared from preferredmacromonomers. In one embodiment, a preferred multifunctionalmacromonomer is provided that includes a copolymeric random alkyleneoxide moiety of the formula:XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Ywherein the mole ratio of m:n is within a range of about 1:9 to about9:1, R¹ is a (C1-C4)alkyl group, and X and Y are independently selectedfrom the group consisting of

wherein R² is H or CH₃ (i.e., “Me”), R³ is an aromatic group, aliphaticgroup, alicylic group, or combinations thereof, and W is an alkylene oralkylene oxide group.

In another preferred embodiment, a multifunctional macromonomer includesa copolymeric random alkylene oxide moiety of the formula:XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Ywherein the mole ratio of m:n is within a range of about 1:9 to about9:1, R¹ is a (C1-C4)alkyl group, and X and Y are independently selectedfrom the group consisting of

wherein R² is H or Me and r=2-10.

In another preferred embodiment, a multifunctional macromonomer includesa copolymeric random alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1 and R¹ is a (C1-C4)alkyl group, and wherein the macromonomer furtherincludes two or more end groups selected from the group consisting of

and mixtures thereof, wherein R² is H or CH₃, R³ is an aromatic group,aliphatic group, alicylic group, or combinations thereof, and W is analkylene or alkylene oxide group.

In another preferred embodiment, a multifunctional macromonomer includesa copolymeric random alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1 and R¹ is a (C1-C4)alkyl group, and wherein the macromonomer furtherincludes two or more end groups selected from the group consisting of

and mixtures thereof, wherein R² is H or Me and r=2-10.

The present invention also provides a syrup polymer mixture thatincludes a partially polymerized homopolymer or copolymer prepared frommonomers including: about 0.1 wt-% to 100 wt-% of a multifunctionalpoly(alkylene oxide) free-radically polymerizable macromonomer having aweight average molecular weight of at least about 2000, wherein themultifunctional poly(alkylene oxide) macromonomer includes a copolymericalkylene random oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1; and R¹ is a (C1-C4)alkyl group; 0 wt-% to about 80 wt-% of amonofunctional poly(alkylene oxide) monomer; 0 wt-% to about 40 wt-% ofa polar monomer; and 0 wt-% to about 20 wt-% of a hydrophobic monomer.The present invention also provides a method of making a gel, the methodincludes forming a syrup polymer mixture as described above; and forminga gel from the syrup polymer mixture.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a cross-section of a wound dressing of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The gel material of the present invention can be used in medicalarticles. Preferably, the gel material is absorbent. Preferably, the gelmaterial of the present invention is advantageously transparent, whichallows for inspection of an underlying material. Significantly, formedical articles, particularly wound dressings, this allows for visualinspection of the wound without removal of the wound dressing. Morepreferably, the gel material is both absorbent and transparent.

Preferred medical articles, particularly wound dressings, of the presentinvention advantageously: can remove excess exudate from the wound;maintain a moist wound environment; allow gas exchange so that oxygen,water vapor, and carbon dioxide can pass through the article; arethermally insulating to maintain the wound at body temperature; may beimpermeable to liquids and microorganisms to minimize contamination andinfection; may be non-adherent to the wound so that no damage is done tothe granulating tissue; and minimize the need to cleanse the wound ofdressing material.

The material is preferably absorbent in that it is capable of absorbingfluids, preferably moderate to heavy amounts of fluids such as bodyfluids, while retaining its structural integrity (and preferably itstransparency). Preferably, herein, “absorbent” refers to a material thatwill absorb at least its own weight of an isotonic saline solution (0.9wt-% sodium chloride in deionized water) after 24 hours at roomtemperature. That is, the material has an absorbency of at least 100%.More preferably, the gel material can absorb at least two times itsweight (200% absorbency), even more preferably at least four times itsweight (400% absorbency), and most preferably at least five times itsweight (500% absorbency) of an isotonic saline solution after 24 hoursat room temperature. Typically, gel material of the present inventioncan absorb up to eight times its weight of an isotonic saline solution.

Preferably, the gel material of the present invention is transparentwhether dry or swollen with an aqueous solution (e.g., bodily fluid).Preferably, herein, transparent refers to a material having a totallight transmittance of greater than 84% per ASTM D1003-00.

Preferred gel materials of the present invention are also be relativelyflexible. Flexibility allows for a medical article incorporating the gelmaterial to be easily applied to a bend portion of a body, such as ajoint, etc. Nonflexible gel materials are also within the scope of thepresent invention. Such gel materials can be used as wound packingmaterials, for example.

The gel material of the present invention is also preferablybiocompatible. Herein, “biocompatible” means that the material can be incontact with bodily tissues (including fluids) without adversereactions. Typically, this occurs if the residual monomers used toprepare the polymer used in the gel material are present in less thanabout 1 percent by weight (wt-%) each, based on the total weight of thepolymer.

The gel material of the present invention can also possess pressuresensitive adhesive properties. The pressure sensitive adhesives of theinvention are polymers exhibiting a glass transition temperature of lessthan −15° C.

Preferably, the polymer used in the gel material of the presentinvention is inherently bacteriostatic and possesses low odor.Alternatively, bacteriostatic or odor removing agents can be added tothe polymer to enhance these properties of the gel material. Suchmaterials are described in greater detail below.

The gel material of the present invention includes a polymer, which canbe a homopolymer or a copolymer, of a multifunctional poly(alkyleneoxide) free-radically polymerizable macromonomer. The multifunctionalpoly(alkylene oxide) macromonomer has a weight average molecular weightof at least about 2000. Preferably, the multifunctional poly(alkyleneoxide) macromonomer includes a copolymeric alkylene oxide moiety of theformula (Formula I):—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1 (preferably, within a range of about 1:5 to about 1:1); and R¹ is a(C1-C4)alkyl group, which can be linear or branched. The distribution ofthe alkylene oxide moieties is random (i.e., there is a relativelyrandom structural distribution of at least two different moieties). Suchmacromonomers are hydrophilic.

In the multifunctional macromonomers of Formula I, a ratio of belowabout 1:9 tends to render the material crystalline, whereas a ratio ofgreater than about 1:1 tends to reduce the absorbency of the material.Also, the longer the alkyl group (R¹), the lower the absorbency of thematerial. Preferably R¹ is a C1 alkyl and the copolymeric alkylene oxidemoiety is a poly(ethylene oxide-co-propylene oxide).

The multifunctionality of the material leads to crosslinking uponpolymerization. Typically, the higher the molecular weight, the greaterthe distance between crosslinks (i.e., the lower the crosslink density),which leads to better mechanical properties. That is, the materials ofthe present invention possess an advantageous balance of compliance(i.e., elasticity) and tensile strength as well as cohesive strength inthe swollen form as a result of the use of the multifunctionalpoly(alkylene oxide) macromonomer.

As stated above, the multifunctional macromonomer has a weight averagemolecular weight of at least about 2000. Macromonomers with molecularweights lower than this tend to form brittle polymers. Preferably themultifunctional macromonomer has a weight average molecular weight of atleast about 4000, more preferably at least about 6000, and mostpreferably at least about 10,000. Such materials can have significantlyhigher molecular weights as well. Preferably, such multifunctionalmacromonomers have a molecular weight such that they are flowable andprocessable at room temperature. High molecular weight multifunctionalmacromonomers that are not flowable at room temperature can be used ifthey can be processed using diluents or other additives and/or highertemperatures (e.g., extrusion temperatures). Most preferably, usefulmultifunctional macromonomers are liquid at room temperature.

Herein, multifunctional means that the macromonomer has more than onereactive group that is free radically polymerizable. Preferably, thereare two or three reactive groups, and more preferably two reactivegroups. Such multifunctional macromonomers can be linear or branched,preferably they are linear.

Preferably, the free radically polymerizable functionality of themultifunctional macromonomer includes ethylenic unsaturation. Examplesof suitable ethylenically unsaturated groups include (meth)acryloyl,(meth)acrylamido, allyloxy, vinyl, etc., as well as combinationsthereof. Alternatively, the reactive groups can include photoinitiatorgroups. Examples of photoinitiator groups include those derived from1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(IRGACURE 2959) or any photoinitiator with a reactive nucleophilicgroup, such as 4-(2-hydroxyethoxy)benzophenone.

Preferably, the multifunctional macromonomer is difunctional. Aparticularly preferred difunctional macromonomer is of the formula(Formula II):XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Ywherein: R¹, m, and n are as defined above; and X and Y are eachindependently selected from the group consisting of

wherein R² is H or CH₃, R³ is an aromatic group, aliphatic group,alicylic group, or combinations thereof, W is an alkylene or alkyleneoxide group, and r=2-10.

Preferably, the R³ groups are derived from diisocyanates. Morepreferably, R³ is selected from the group consisting of —(CH₂)_(p)—wherein p=1-18, tolylene, and

Most preferably, R³ is derived from toluene diisocyanate, hexamethylenediisocyanate, or H₁₂-MDI (4,4′-methylene bis(cyclohexyl)diisocyanate).

Preferably, W is an alkylene or alkylene oxide containing up to 100carbon atoms. More preferably, W is a group derived from an hydroxyalkyl(meth)acrylate.

As with Formula I, the alkylene oxide moieties of Formula II are random.More preferably, it is a random poly(ethylene oxide-co-propyleneoxide)-containing macromonomer.

The multifunctional macromonomers can also be tri-, tetra-,penta-functional, etc., macromonomers. Such compounds also include acopolymeric random alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—wherein the mole ratio of m:n is within a range of about 1:9 to about9:1; and R¹ is a (C1-C4)alkyl group, and two or more end groups selectedfrom the list of X and Y groups above. It should be understood that suchend groups would be bonded through oxygen.

Multifunctional macromonomers can be linear with branched end groups orcan be branched through a central core. Branched macromonomers can beprepared, for example, by chemical modification of linear dihydroxyterminated alkylene oxide random copolymers to produce multiple reactiveend groups at each chain end. For example, a macromonomer with twopolymerizable groups at each chain end can be prepared by reacting alinear dihydroxy terminated alkylene oxide random copolymer withtrimellityl chloride followed by reaction with 2-hydroxyethylmethacrylate. Branch points in the macromonomer can also be introducedthrough incorporation of a central core. Examples of such materialsinclude, but are not limited to, ethoxylated/propoxylateddipentaerythritol, pentaerythritol, and trimethyolpropane that have beenfurther reacted with reactive ethylenically unsaturated compounds.

It should also be understood that each arm of a multifunctionalmacromonomer includes the copolymeric random alkylene oxide moiety,although each arm in any one macromonomer can be different. Also, therecan be other groups or linkages, such as urethanes and/or urea groupsbetween various copolymeric random alkylene oxide moieties in any onearm.

A particularly preferred macromonomer is of the formulaXO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Ywherein R¹ is methyl, the mole ratio of m:n is about 1:3, and X and Yare each independently

wherein R² is CH₃. This is referred to herein as MAA-PEG.

The functional macromonomers can be prepared, for example, by reactingdihydroxy terminated alkylene oxide random copolymers (which aretypically commercially available such as poly(ethyleneoxide-co-propylene oxide) commercially available as UCON-75H-90,000 fromDow Chemical Co., Midland, Mich.) with reactive ethylenicallyunsaturated compounds (e.g., acrylates) or photoinitiators. A variety ofreactive ethylenically unsaturated compounds such as acrylatederivatives can be used including, but not limited to, (meth)acrylicacid, (meth)acryloyl chloride, (meth)acrylic anhydride, and2-isocyanatoethyl (meth)acrylate. In addition, the dihydroxy terminatedalkylene oxide random copolymer can be reacted with a diisocyanate, suchas isophorone diisocyanate, resulting in an isocyanate terminatedfunctional random copolymer that is further reacted with eitherfunctional (meth)acrylates or photoinitiators such as2-hydroxyethyl(meth)acrylate or1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one.Preferably, the functional macromonomer is prepared by reacting thehydroxy terminated alkylene oxide random copolymer with methacrylicanhydride. Typically, if a stoichiometric amount of the ethylenicallyunsaturated reactant is combined with the dihydroxy terminated alkyleneoxide random copolymer, 100% conversion to the disubstituted product isobtained. However, if less than a stoichiometric amount is used, theproduct is typically a mixture of disubstituted and monosubstitutedproducts and possibly some dihydroxy terminated starting material. Suchmixtures tend to provide gels with higher absorbency.

A multifunctional macromonomer as described herein can behomopolymerized or copolymerized with other multifunctionalmacromonomers or other hydrophilic monomers to enhance the absorbency ofthe polymer used in forming the gel material. Examples of suitablehydrophilic monomers include monofunctional poly(alkylene oxide)monomers and other polar monomers. The multifunctional macromonomer (orcombination of macromonomers) can be copolymerized with hydrophobicmonomers also to better control the absorbency of the polymer.Combinations of such hydrophilic and hydrophobic monomers can be used ifdesired.

Monofunctional poly(alkylene oxide) monomers can be used to increase theabsorbency of the polymer used in forming the gel material. For certainpreferred embodiments, such monomers can be analogous structurally tothe multifunctional macromonomers described above with only one reactivegroup (e.g., only one (meth)acryloyl group, (meth)acrylamido group,allyloxy group), wherein the other end groups include nonreactive groupssuch as (C1-C4)alkoxy, aryloxy (e.g., phenoxy), (C1-C4)alkaryloxy,ar(C1-C4)alkyloxy, or hydroxy groups. These groups can be linear orbranched.

Preferred monofunctional poly(alkylene oxide) monomers are of theformula (Formula III):H₂C═C(R²)—C(O)-Q-(—CH(R¹)—CH₂—O—)_(x) . . . (—CH₂—CH₂—O—)_(y)-Zwherein the mole ratio of x:y is within a range of 0 to 1; R²═H or CH₃;R¹ is as defined above for Formulas I and II; Z is H or a (C1-C4)alkylgroup, an aryl group, a (C1-C4)alkaryl group, or an ar(C1-C4)alkylgroup; and Q is —O—, —(H)N—C(CH₃)₂—C(O)—O—, —O—CH₂CH₂—N(H)—C(O)—O—, or

wherein R² is H or CH₃, R³ is an aromatic group, aliphatic group,alicylic group, or combinations thereof, and W is an alkylene oralkylene oxide group. These groups can be linear or branched. As withFormulas I and II, the alkylene oxide moieties are random (unless theratio of x:y is 0). Such materials preferably have a weight averagemolecular weight of at least 200. Preferred R³ and W groups are asdescribed above. Preferably, Q is oxygen.

Examples of suitable monofunctional poly(alkylene oxide) monomersinclude poly(ethylene oxide)(meth)acrylate, poly(propyleneoxide)(meth)acrylate, poly(ethylene oxide-propyleneoxide)(meth)acrylate, and combinations thereof. Such monomers typicallyinclude nonreactive end groups such as (C1-C4)alkoxy, aryloxy (e.g.,phenoxy), (C1-C4)alkaryloxy, ar(C1-C4)alkyloxy, or hydroxy groups. Thesegroups can be linear or branched. These monomers can be of a wide rangeof molecular weights and are commercially available from sources such asSartomer Company, Exton, Pa.; Shinnakamura Chemical Co., Ltd., Tokyo,Japan; Aldrich, Milwaukee, Wis.; and Osaka Organic Chemical Ind., Ltd.,Osaka, Japan.

Polar monomers other than the poly(alkylene oxide) monomers can also beused to increase the absorbency of the polymer used in forming the gelmaterial. Preferred polar monomers can also provide compliance to theresultant polymer. Examples of suitable polar monomers include2-hydroxyethyl(meth)acrylate (HEMA), 2-hydroxypropyl(meth)acrylate,3-hydroxypropyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, N-vinylcaprolactam, N-vinyl acetamide, N-vinyl pyrrolidone, acrylamide, mono-or di-N-alkyl substituted acrylamide, (meth)acrylic acid, itaconic acid,beta-carboxyethyl acrylate, glycerol methacrylate,[2-(meth)(acryloyloxy)ethyl]trimethylammonium chloride,[2-(meth)(acryloyloxy)ethyl]trimethylammonium methyl sulfate, andcombinations thereof. Preferred polar monomers include2-hydroxyethyl(meth)acrylate (HEMA) and N-vinyl pyrrolidone.

Hydrophobic monomers can be used to reduce (and thereby better control)the absorbency of the polymer used in forming the gel material, andpreferably improve the strength of the polymer. Examples of suitablehydrophobic monomers include (meth)acrylic acid esters such as laurylacrylate, 2-ethylhexyl acrylate, and isooctyl acrylate, as well asalpha-methylstyrene, and combinations thereof.

Preferred polymers used in forming the gel materials of the presentinvention include at least about 0.1 wt-% of the multifunctionalpoly(alkylene oxide) macromonomer, based on the total weight of thepolymer. Practically, there is no upper limit to the amount of thismultifunctional macromonomer that can be used. For example, homopolymersare possible, which could include 100 wt-% of any one multifunctionalmacromonomer. Preferred polymers for use in gel materials of the presentinvention include at least about 5 wt-% of the multifunctionalpoly(alkylene oxide) macromonomer, based on the total weight of thepolymer. More preferably, the multifunctional poly(alkylene oxide)macromonomer is used in an amount of no greater than about 60 wt-%,based on the total weight of the polymer. Most preferably, themultifunctional poly(alkylene oxide) macromonomer is used in an amountof no greater than about 20 wt-%, based on the total weight of thepolymer.

Preferred polymers used in forming the gel materials of the presentinvention include no greater than about 80 wt-% of a monofunctionalpoly(alkylene oxide) monomer, based on the total weight of the polymer.More preferably, the monofunctional poly(alkylene oxide) monomer is usedin an amount of at least about 30 wt-%, based on the total weight of thepolymer. Most preferably, the monofunctional poly(alkylene oxide)monomer is used in an amount of at least about 40 wt-%, based on thetotal weight of the polymer.

Preferred polymers used in forming the gel materials of the presentinvention include no greater than about 40 wt-% of a polar monomer,based on the total weight of the polymer. More preferably, the polarmonomer is used in an amount of no greater than about 35 wt-%, based onthe total weight of the polymer. Most preferably, the polar monomer isused in an amount of no greater than about 30 wt-%, based on the totalweight of the polymer. Preferably, the polar monomer is used in anamount of at least about 5 wt-%, based on the total weight of thepolymer. More preferably, the polar monomer is used in an amount of atleast about 10 wt-%, based on the total weight of the polymer.

Preferred polymers used in forming the gel materials of the presentinvention include no greater than about 20 wt-% of a hydrophobicmonomer, based on the total weight of the polymer. More preferably, thehydrophobic monomer is used in an amount of less than 20 wt-%, based onthe total weight of the polymer. Even more preferably, the hydrophobicmonomer is used in an amount of no greater than about 10 wt-%, based onthe total weight of the polymer. Most preferably, the hydrophobicmonomer is used in an amount of no greater than about 5 wt-%, based onthe total weight of the polymer.

The polymer used in forming the gel material of the present invention(and preferably the gel material as well) is preferably substantiallyacid free. By this it is meant that no acidic monomers (e.g.,(meth)acrylic acid, itaconic acid) are used in preparing the polymer inthe gel material, although there may be certain acidic monomers presentas contaminants in other monomers used. Thus, “substantially acid free”means that less than about 2 wt-% of the monomers used to prepare thepolymer are acidic monomers.

The polymer used in forming the gel material of the present inventioncan be produced by polymerizing the above-described monomers byconventional polymerization methods. Typical polymerization methods thatcan be used include thermal and/or photochemical as well as bulk andsolution polymerization.

In a typical solution polymerization method, a monomer mixture is heatedwith stirring in the presence of a solvent and a polymerizationinitiator. Examples of the solvent are methanol, ethanol, isopropanol,acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, toluene,xylene, and an ethylene glycol alkyl ether. Those solvents can be usedalone or as mixtures thereof. Examples of the polymerization initiatorare benzoyl peroxide, cumene hydroperoxide, diisopropylperoxydicarbonate, and azobisisobutyronitrile. Those polymerizationinitiators can be used alone or as mixtures thereof.

In a typical photopolymerization method, a monomer mixture is irradiatedwith ultraviolet (UV) rays in the presence of a photopolymerizationinitiator (i.e., photoinitiators). Preferred photoinitiators are thoseavailable under the trade designations IRGACURE and DAROCUR from CibaSpeciality Chemical Corp., Tarrytown, N.Y. and include 1-hydroxycyclohexyl phenyl ketone (IRGACURE 184),2,2-dimethoxy-1,2-diphenylethan-1-one (IRGACURE 651),bis(2,4,6-trimethylbenzoyl)phenylphosphineoxide (IRGACURE 819),1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propane-1-one(IRGACURE 2959), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butanone(IRGACURE 369),2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one (IRGACURE907), and 2-hydroxy-2-methyl-1-phenyl propan-1-one (DAROCUR 1173).Particularly preferred photoinitiators are IRGACURE 819 and 2959.

A particularly preferred method of forming the polymer is described inU.S. Patent Publication No. 2003-0194526 and entitled METHOD OF MAKING AVISCOELASTIC ARTICLE BY COATING AND CURING ON A REUSABLE SURFACE.

Preferably, the method involves a “syrup polymer” technique, by whichthe polymer is dissolved in the component monomers, which react into thepolymer backbone, further increasing the molecular weight. Molecularweight may be controlled through the use of chain transfer agents andchain retarding agents, as are known in the art, such as alkylmercaptans such as dodecyl mercaptan, isooctyl thioglycolate, andalpha-methylstyrene.

Thus, the present invention also provides a syrup polymer mixture andthe polymerized product thereof. The syrup polymer mixture preferablyincludes: about 0.1 wt-% to 100 wt-% of a solute polymer having terminalor pendant reactive free-radically curable functional groups (i.e., themultifunctional poly(alkylene oxide) macromonomer described above); 0 toabout 80 wt-% of a monofunctional poly(alkylene oxide) monomer; 0 toabout 40 wt-% of a polar monomer (distinct from the monofunctionalpoly(alkylene oxide) monomer); and 0 to about 20 wt-% of a hydrophobicmonomer. Such a syrup is preferably partially polymerized (typically,about 10-15% conversion) to form a coatable composition (typically,having a viscosity of about 300 centipoise to about 20,000 centipoise),then coated onto a backing or a release liner, for example, and thenpolymerized further to form a gel. The syrup polymer mixture preferablyincludes a photoinitiator. The step of forming a gel from the syruppolymer mixture preferably includes applying radiation (infrared,ultraviolet, visible, electron beam, etc., preferably, ultravioletradiation), thermal energy, or a combination thereof (preferablysequentially).

The gel material of the present invention can include one or more activeagents, such as pharmacologically active agents. Examples include, butare not limited to, growth factors (e.g., TGF, FGF, PDGF, EGF, etc.),antibacterial agents (e.g., penicillins, neomycin sulfate,sulphonamides, sulfadiazine, silver sulfadiazine, trimethoprim, andother antibiotics, as well as povidone iodine, iodine, silver, silverchloride, and chlorhexidine), antifungal agents (e.g., griseofulvin,chlormidazole hydrochloride, clotrimazole, ketoconazole, miconazole,miconazole nitrate, nistatin, and tolnaftate), disinfectants andantiseptics (e.g., benzalkonium chloride, cetalkonium chloride,chlorhexidine gluconate, ethanol, iodine, methylbenzethonium, povidoneiodine, isopropanol, silver, silver oxide, silver salts such as silverlactate and silver chloride, triclosan), local anaesthetics (e.g.,tetracaine, benzocaine, prilocalne, procaine), debriding agents,anti-inflammatory agents (e.g., indomethacin, ketoprofen, dichlofenac,ibuprofen, etc.), astringents, enzymes, nutrients (e.g., vitamins,minerals, oxygen, etc.), drugs for cataplasms (e.g., menthol, camphor,peppermint, capsicum extract, capsaicin, etc.), and odor absorbingagents (e.g., zeolites, silicates, chitosans, cyclodextrins, etc.).Preferred active agents are antibacterial agents such as povidoneiodine, iodine, silver, silver chloride, and chlorhexidine. Activeagents can be used alone or as mixtures thereof. They can be addedbefore or after the reaction product of this invention is cured as longas they do not interfere with polymerization of the polymer. Preferably,they are added in an amount or manner that does not interfere with thefunction or clarity of the finished gel material.

Optionally, the gel material of the present invention can includehydrocolloids, typically in the form of particles, although they are notnecessarily preferred since they can diminish the transparency of thegel material. Examples of hydrocolloids include, but are not limited to,natural gums, such as plant exudates (gum arabic, ghatti, karaya, andtragacanth); plant seed gums (guar, locust bean and acacia), seaweedextracts (agar, algin, alginate salts and carrageenin), cereal gums(starches and modified starches), fermentation or microbial gums(dextran and xanthan gum), modified celluloses (hydroxymethylcellulose,microcrystalline cellulose and carboxymethylcellulose) pectin, gelatin,casein and synthetic gums (polyvinylpyrrolidone, low methoxyl pectin,propyleneglycol alginates, carboxymethyl locust bean gum andcarboxymethyl guar gum) and like water-swellable or hydratablehydrocolloids. The term hydrocolloid is used regardless of the state ofhydration. The gel material of the present invention preferably includesan amount of the hydrocolloid such that the material is transparent(preferably, the total light transmittance is greater than 84% per ASTMD1003-00). Typically, the amount of hydrocolloid, if used, is less thanabout 5 wt-%, based on the total weight of the gel material.

Other additives that can be incorporated into the gel material of thepresent invention include: viscosity modifiers (e.g., polymericthickeners such as that commercially available under the tradedesignation GANTREZ resin from International Specialty Products, Wayne,N.J.); chain transfer or retarding agents (e.g., such as alkylmercaptans such as dodecyl mercaptan, isooctyl thioglycolate, andalpha-methylstyrene, the latter of which can also be a hydrophobicmonomer as discussed above); colorants; indicators; tackifiers;plasticizers (e.g., water, glycerin, polyethylene oxide, polypropyleneoxide, and mixtures thereof such as those commercially available underthe trade designation PLURONICS from BASF Co., as well as various lowmolecular compounds capable of plasticizing the polymer); àntioxidants;etc. Such additives can be added either before or after thepolymerization using techniques known to one of skill in the art.Preferably, if used, they can be added in an amount and manner that doesnot interfere with the function or clarity of the gel material.

Preferably, the gel material of the present invention is substantiallyfree of plasticizers, including water. This is advantageous at leastbecause special packaging is not required. Furthermore, plasticizers canmigrate to other parts of a dressing, for example, which can bedetrimental to the integrity of the dressing, or into the body of thepatient on which the dressing is disposed.

Optionally, the gel material may have a patterned surface on at leastone major surface thereof. The patterned surface allows greater surfacearea for absorption of wound exudate when oriented toward the woundsurface, while reducing the absorbent surface area in direct or indirectcontact with the wound. More significantly, the patterned surfacereduces the propensity of the absorbent layer to swell and push againstthe wound, avoids mushrooming (i.e. expansion of the gel layer through aporous film) and further avoids premature separation of an adhesivelayer from the skin.

The optional pattern imparted to the surface of a layer of the gelmaterial may be any suitable preselected three-dimensional pattern.Preferably, the pattern is one that increases the surface area availablefor absorption and reduces swelling into the wound, retards mushrooming,and/or enhances integrity of the material upon hydration. The patterncan include an array of pattern elements that include, but are notlimited to, ridges, channels, mounds, peaks, hemispheres, pyramids,cylinders, cones, blocks, and truncated variations and combinationsthereof. The pattern may further include apertures having apredetermined shape and size extending through the thickness of theabsorbent layer.

The specific pattern element is advantageously chosen to present minimalsurface area in contact with a wound or the facing film if present. Theminimal surface area further retards the tendency of the gel material toswell into the wound, mushroom, or adhere to the wound site. Especiallyuseful elements include pyramids, cones and truncated versions thereof,and ridges which are triangular in cross section. The elements may berandom or non-random in the x direction, the y direction, or both. Forease of manufacture, it is preferable that the pattern comprises anon-random array of elements disposed on the surface of the gel.

If desired, a pattern may also be imparted to the outer face of the gellayer (i.e., the major surface of the gel layer that faces away from thewound surface). Imparting such a pattern increases the surface area ofthe gel layer and may promote greater evaporation of the fluid from thegel material. The pattern may be the same or different than the patternon the facing surface of the gel material, as can the size of thepattern elements. Further, the individual elements on either surface ofthe gel material may be protuberances extending form the surface, or maybe depressions in the surface.

If desired, the gel material may be in direct contact with the woundand/or skin surface. However, direct contact may be provided by othersuitable hydrocolloid and hydrogel absorbent materials.

In a preferred medical article, the gel material forms a layer that isgenerally about 250 micrometers (i.e., microns) to about 5000micrometers in total thickness.

Optionally, a wound dressing of the invention may include at least twoabsorbent layers: a first absorbent layer and a second absorbent layer.The first absorbent layer is typically more absorbent than the secondabsorbent layer, and can retain a greater volume of body fluids than thesecond absorbent layer. The second absorbent layer is positioned suchthat it is located between the first absorbent layer and the wound. Thissecond absorbent layer provides integrity to the wound dressing andavoids transfer of the first absorbent layer into the wound.

The first absorbent layer typically contains the polymer described aboveprepared from the multifunctional macromonomer. The second absorbentlayer is typically positioned in contact with the first absorbent layerand is typically less absorbent of body fluids than the first absorbentlayer. The second absorbent layer can contain the reaction product of anacrylic acid ester of a non-tertiary alcohol having from 4 to 14 carbonatoms; a hydrophilic, ethylenically unsaturated monomer; and a polar,ethylenically unsaturated monomer, although other compositions can beused in the second absorbent layer.

Generally, the second absorbent layer functions as a “barrier” betweenthe first absorbent layer (which may partially “disintegrate” whenexudate is unevenly, rapidly absorbed or when it absorbs more than about500%) and the wound. Preferably the second absorbent layer has adhesiveproperties (or is a pressure sensitive adhesive) and functions toenhance the overall integrity of the wound dressing. In this regard, thesecond absorbent layer ties the first absorbent layer to a wound-facinglayer (or to the wound itself). By having adhesive properties, thissecond absorbent layer not only aids in controlling the absorption ofexudate, but also physically joins other components of the dressing.

As stated above, the first absorbent layer is typically significantlymore absorbent than the second absorbent layer, and preferably has anabsorbency at least 100 percent greater than the absorbency of thesecond absorbent layer. The first absorbent layer preferably absorbs atleast 400 percent of its weight after immersion in an isotonic salinesolution after 24 hours at room temperature.

A typical wound dressing of the present invention preferably includes aporous or non-porous facing layer to provide a fluid permeable barrierbetween the wound site and the gel layer. The facing layer allowstransport of moisture (i.e. fluid and vapor) from the wound to the gellayer and may isolate the wound from other components of the dressing.The facing layer is preferably soft, flexible, conformable,non-irritating and non-sensitizing. Any of a variety of polymers may beused including polyurethane, polyethylene, polypropylene, polyamide orpolyester materials. Further, the facing layer may be in the form ofmoisture vapor permeable films, perforated films, woven-, non-woven orknit webs or scrims. A preferred facing layer comprises a polyurethanefilm.

In one useful embodiment, the facing layer is conformable to animal(including human) anatomical surfaces, has a moisture vapor transmissionrate (MVTR) of at least 300 grams per square meter per 24 hours at 80%relative humidity differential at 40° C. (per method of Chen, U.S. Pat.No. 5,733,570), is impermeable to liquid water throughout substantiallyits entire imperforate area and contains perforations means for passingwound exudate through the facing layer. This means that the facing layerdoes not pass liquid water under normal wound treatment conditionsexcept at the places in the facing layer that are positively perforatedto allow the exudate to pass into the reservoir.

The preferred moisture vapor transmission rate of the facing layer is atleast 600 grams per square meter per 24 hours at an 80% relativehumidity differential at 40° C. The facing layer may further comprise apressure sensitive adhesive layer. The adhesive coated facing layerpreferably has the aforesaid MVTR. Therefore, if the facing layer isimpermeable to liquid water except for the perforation means, theadhesive can be permeable to liquid water and vice versa. Porous ornon-porous facing layers such as perforated polyamide, polyester,polypropylene, polyethylene, polyether-amide, polyurethanes, chlorinatedpolyethylene, styrene/butadiene block copolymers (KRATON brandthermoplastic rubber, Shell Chemical Company, Houston, Tex.) andpoly(vinyl chloride) and those described in U.S. Pat. No. 3,121,021(Copeland) that are covered with a pressure sensitive adhesive that isnot permeable to liquid water can be used for the facing layer.Optionally these films can be perforated. Additional porous materialsinclude woven and non-woven substrates.

It is preferred that the facing layer have the above mentioned moisturevapor or liquid permeability (1) so that maceration of the skin underthe wound dressing does not occur, (2) so that moisture build-up underthe facing layer does not cause the facing layer and, therefore, wounddressing to be lifted off the skin, and (3) to enhance proximation ofthe wound edges. Preferred facing layers are thin polymeric filmsoptionally coated with pressure sensitive adhesive which, incombination, have the above characteristics.

The perforation means in the facing layer are holes or slits or otherperforations that conduct the passage of liquid water or wound exudatefrom the wound into the absorbent layer of the wound dressing. Theperforations may additionally extend through an adhesive layer, if thefront surface of the facing film (that surface facing toward the wound)is coated with a pressure sensitive adhesive layer.

A backing layer may be present in all of the embodiments of the presentinvention. Preferably the backing layer is conformable to animalanatomical surfaces, impermeable to liquid water and has a moisturevapor transmission rate of at least 600 grams per square meter per 24hours at an 80% relative humidity differential at 40° C. The backinglayer, in combination with a facing layer, may be constructed to form areservoir (e.g., a pouch or envelope) that surrounds the gel layer, intowhich the exudate from the wound passes. This reservoir does not permitliquid water or exudate to pass out of it. Instead, the gel layerabsorbs the exudate, and moisture in the exudate passes through thebacking layer in a vapor form into the atmosphere. The reservoirdressing permits wound exudate to be rapidly removed from the wound siteand prevents liquids or bacteria from outside the dressing tocontaminate the wound site.

In order to remove moisture vapor, the moisture vapor transmission rateof the backing layer is at least as above noted, and preferably at least1200 grams per square meter per 24 hours at an 80% relative humiditydifferential at 40° C.

The preferred embodiments for the facing and backing layers are thinconformable polymeric films. Generally the films are about 12 microns toabout 50 microns in thickness, preferably about 12 microns to about 25microns. Conformability is somewhat dependent on thickness, thus thethinner the film the more conformable the film. Reference has been madeherein to the films utilized in the medical article (e.g., wounddressing) of the present invention being conformable to animalanatomical surfaces. This means that when the films of the presentinvention are applied to an animal anatomical surface, they conform tothe surface even when the surface is moved. The preferred films areconformable to animal anatomical joints. When the joint is flexed andthen returned to its unflexed position, the film stretches toaccommodate the flexation of the joint but is resilient enough tocontinue to conform to the joint when the joint is returned to itsunflexed condition.

Examples of films which are useful in applicant's invention as facing orbacking layers include polyurethanes such as those available under thetrade designation ESTANE from B.F. Goodrich, Cleveland, Ohio,elastomeric polyester such as those available under the tradedesignation HYTREL from E.I. duPont deNemours & Co., Wilmington, Del.,blends of polyurethanes and polyesters, polyvinyl chlorides, andpolyether-amide block copolymers such as those available under the tradedesignation PEBAX available from Elf-Atochem. Particularly preferredfilms for use in the present invention are polyurethane and elastomericpolyester films. The polyurethane and elastomeric polyester filmsexhibit a resilient property that allows the films to have goodconformability.

Particularly useful films include “spyrosorbent” films having adifferential moisture vapor transmission rate (MVTR). Dressingsincorporating spyrosorbent films not only manage wound exudate byabsorption, but have the ability to adjust the moisture vaportransmission properties in response to the amount of exudate. Suchspyrosorbent films are hydrophilic, moisture vapor permeable and have arelatively high MVTR (wet), and have a differential MVTR ratio (wet todry) that is greater than 1, and preferably greater than 3:1. The dryMVTR is greater than about 2600 g/m²/24 hrs, preferably about 3000 to4000 g/m²/24 hrs. A particularly preferred spyrosorbent film, useful asa backing layer, is a segmented polyurethane such as a segmentedpolyether polyurethane urea based on polytetramethylene glycol andpolyethylene glycol polyols. Such a spyrosorbent films are described inU.S. Pat. Nos. 5,653,699 and 4,849,458 (Reed et al.).

Another suitable backing layer is a fluid control film having at leastone microstructures-bearing surface with channels that permitdirectional control of a liquid. This film can be used to transport afluid to a remote site and thereby facilitate wicking away of a fluid(e.g., wound exudate). Such a film is disclosed in InternationalPublication No. WO 00/42958.

Many different constructions of a wound dressing are possible with thefacing layer, the gel layer, and the backing layer. In one embodiment,the areas of the facing layer and the backing layer are greater thanthat of the gel layer and the facing layer is bonded to the backinglayer, thereby forming a pouch, with the gel disposed between the two.In another embodiment, one of the facing or backing layers may besubstantially the same area as the gel layer, and the other of greaterarea. The greater area of the facing or backing layer forms a peripheryto which an adhesive layer and a release liner may be attached. It willfurther be understood that the facing and/or backing layer may beattached or bonded to the adjacent surface of the gel layer to form acontiguous layer construction, in which the backing and facing layersmay be the same or of greater area than the gel layer. Alternatively,the backing and facing layers may be bonded to each other, and may ormay not be bonded to the gel layer. In these last constructions, the gellayer is constrained within a pouch created by the attachment of thefacing and backing layers to each other. The layers may be bonded toeach other by any conventional means such as adhesives, heat sealing, orother bonding means.

It is preferred that the facing and backing layers of the medicalarticles of the present invention be at least translucent and morepreferably sufficiently transparent so that the wound site to which theyare applied can be viewed through the medical article. It isadvantageous to view and evaluate the wound and healing thereof withoutremoval of the wound dressing to avoid unnecessary handling of the woundsite and exposure of the wound to the environment, which reduces thelikelihood of contamination, and avoids the need to cleanse the wound aswould be the case were the dressing to be removed. It is preferred thatthe dressing be both transparent and colorless so that the color of thewound, exudate, and periwound skin may also be evaluated. Preferredtransparent films for use as facing and backing layers that allow visualinspection of the wound site include polyurethane films such as thoseavailable under the trade designation ESTANE from B.F. Goodrich,Cleveland, Ohio; elastomeric polyesters such as those available underthe trade designation HYTREL from E.I. duPont deNemours & Co.,Wilmington, Del.; and, polyether block amides such as those availableunder the trade designation PEBAX from Elf Altochem North America,Philadelphia, Pa. Other useful films are those describes in U.S. Pat.No. 4,499,896 (Heinecke); U.S. Pat. No. 4,598,004 (Heinecke); and U.S.Pat. No. 5,849,325 (Heinecke et al).

While the facing layer can be attached to the wound by means other thana pressure sensitive adhesive on its surface, it is preferred to usesuch an adhesive. The presence of the adhesive of the facing layernormally reduces the moisture vapor permeability of the facing layer.Therefore it is preferred that the facing layer is adhesive coated priorto adding a plurality of perforations to the layer. The wound exudatetherefore can readily pass through a perforated adhesive coated facinglayer. Preferably, both the facing and backing layers are precoated withan adhesive layer to both facilitate bonding of the backing layer to thefacing layer (forming a pouch), and bonding of the facing film to thewound site.

The facing layer is normally attached to the wound site by means ofadhesive which can be continuous or pattern coated. The preferredadhesive which can be used with the wound dressings of present inventionare the normal adhesives which are applied to the skin such as thosedescribed in U.S. Pat. No. Re. 24,906 (Ulrich), particularly a copolymerof 96% iso-octyl acrylate units and 4% acrylamide units and a copolymerof 94% iso-octyl acrylate units and 6% acrylic acid units. Other usefuladhesives are those described in U.S. Pat. No. 3,389,827 that compriseblock copolymers having three or more polymer block structures having ageneral configuration --A--B--A--- wherein each A is a thermoplasticpolymer block with a glass transition temperature above room temperature(i.e., above about 20° C.) having an average molecular weight betweenabout 5000 and 125,000 and B is a polymer block of a conjugated dienehaving an average molecular weight between about 15,000 and 250,000.Additional examples of useful adhesives are acrylic adhesives such asiso-octyl acrylate/N-vinyl pyrrolidone copolymer adhesives andcrosslinked acrylate adhesives such as for example those described inU.S. Pat. No. 4,112,213 (Waldman). Inclusion in the adhesive ofmedicaments is useful for enhancing wound healing and the inclusion ofantimicrobial agents such as iodine is useful for preventing infection.

The adhesive may optionally be a microsphere adhesive with low traumaproperties as described in U.S. Pat. No. 5,614,310 (Delgado et al.); afibrous adhesive with low trauma properties as described in U.S. Pat.No. 6,171,985 B1 (Joseph et al.); or have especially good adhesion towet skin, such as the adhesives described in U.S. Pat. No. 6,198,016 B1(Lucast et al.), and International Publication Nos. WO 99/13866 and WO99/13865; multilayered adhesives as disclosed in U.S. Pat. PublicationNo. 2001/0051178 A1 (Blatchford et al.). A particularly preferredadhesive includes 15 wt-% acrylic acid, 15 wt-% methoxypolyethyleneoxide 400 acrylate, 70 wt-% isooctyl acrylate, prepared according toExample 1 of U.S. Pat. No. 5,849,325 (Heinecke et al.).

The adhesive may be chosen to be permeable to water or wound exudate, orthe adhesive may be pattern coated on the front surface of the wounddressing (i.e. the surface in contact with the wound site, whether it isthe front surface of the facing or backing layers) so as to not impedethe flow of exudate to the gel layer, i.e. the adhesive may be coated atthe periphery of the wound dressing. Alternatively the adhesive layermay be perforated as described for the facing film to provide a fluidpath for the exudate.

A release liner may be attached to the adhesive layer for ease ofhandling. Examples of release liners are liners made of or coated withpolyethylene, polypropylene and fluorocarbons and silicone coatedrelease papers or polyester films. Examples of the silicone coatedrelease papers are POLYSLIK S-8004, 83 pound (135.4 g/m²) bleachedsilicone release paper supplied by H.P. Smith Co., Chicago, Ill., and 80pound (130.5 g/m²) bleached two-sided silicone coated paper(2-80-BKG-157) supplied by Daubert Chemical Co., Dixon, Ill.

A wound dressing of the present invention may also include a frame thatallows the dressing to be more easily applied to the wound. The framesare made of a relatively rigid material that maintains the shape of thedressing during handling and application to the wound site. The frame isgenerally releasably adhered to the back surface of the backing film andis removed after application of the wound dressing. Suitable frames aredescribed in U.S. Pat. No. 5,531,855 (Heinecke et al.) and U.S. Pat. No.5,738,642 (Heinecke et al.).

An optional patterned surface may be imparted to the gel material byconventional molding techniques. Alternatively, a desired pattern may beimparted using an embossing technique. Examples of such techniques aredescribed in International Publication No. WO 01/60296 A1.

FIG. 1 shows a cross-section of a preferred wound dressing of theinvention. Wound dressing 10 includes a gel layer 12 having a frontsurface 14 and a back surface 16. The gel layer 12 is disposed betweenbacking layer 18 and facing layer 20. As shown, both backing layer 18and facing layer 20 have a greater area than gel layer 12 to form aperiphery 22 at which backing and facing layers may be bonded to eachother. The facing layer 20 is permeable to wound exudate and preferablyhas a plurality of apertures 24 therethrough to conduct exudate from thewound surface to the gel layer 12. Dressing 10 may further include anadhesive layer 26 for securing dressing to the wound site. As depicted,the adhesive layer covers substantially the entire wound-facing surfaceof facing layer 20. In such constructions, it will be understood thatthe apertures would further extend though both the facing layer and theadhesive layer. It will be understood that adhesive layer 26 may becoated on only a portion of the wound dressing. For example, theadhesive layer may be coated on the periphery 22. The wound dressing 10may further comprise a frame 28 to provide temporary support to thewound dressing during application. Frame 28, if present, is generallyremovably adhered to the wound dressing to facilitate removal afterapplication of the wound dressing to the wound site.

EXAMPLES

The following examples are offered to aid in understanding of thepresent invention and are not to be construed as limiting the scopethereof. Unless otherwise indicated, all parts and percentages are byweight.

The following Preparative Examples are directed toward preparingmacromonomers of the formulaXO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Y

wherein X and Y are each independently selected from the groupconsisting of

Acronym X Y R¹ R² R³ m:n W r MAA-PEG Structure 1 Structure 1 CH₃ CH₃ —1:3 — — VAZ-PEG Structure 3 Structure 3 CH₃ — — 1:3 — — IEM-PEGStructure 2 Structure 2 CH₃ CH₃ — 1:3 — 2 IPH1-PEG Structure 4 Structure4 CH₃ CH₃ Isophorone 1:3 (CH₂)₂ — IPH2-PEG Structure 4 Structure 4 CH₃CH₃ Isophorone 1:3 (CH₂)₂ — IPH3-PEG Structure 4 Structure 4 CH₃ CH₃Isophorone 1:3 (CH₂)₂ — TDI-PEG Structure 4 Structure 4 CH₃ CH₃ Tolylene1:3 (CH₂)₂ — PIA-IPDI- Structure 5 Structure 5 CH₃ — Isophorone 1:3 — —PEG

Preparative Examples

Preparation of methacrylated polyalkylene oxide (MAA-PEG). A mixture of218.15 grams (g) of poly(ethylene oxide-co-propylene oxide)(UCON-75H-90,000, Dow Chemical Co., Midland, Mich., number averagemolecular weight by end group analysis of 13,228, and number averagemolecular by Gel Permeation Chromatography (GPC) of 24,153, and weightaverage molecular weigh by GPC of 25,248), 5.4 g of methacrylicanhydride (Aldrich Chemical Co., Milwaukee, Wis.), and 0.11 g of2,6-di-tert-butyl-4-methylphenol (Aldrich Chemical Co., Milwaukee, Wis.)was heated at 100° C. under nitrogen for 12-14 hours with stirring. Theproduct was obtained as a thick yellow liquid (abbreviated hereinafteras “MAA-PEG”).

Synthesis of acrylated polyalkylene oxide (VAZ-PEG). A mixture of3856.52 g poly(ethylene oxide-co-propylene oxide) (UCON-75H-90,000, (DowChemical Co., Midland, Mich.), 82.3 g of vinyl dimethyl azlactone (SNPE,Paris, France) and 1.80 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (AldrichChemical Co., Milwaukee, Wis.) was stirred under nitrogen at roomtemperature for 15 minutes. The temperature was increased to 70° C. andstirring was continued for 48 hours. The product was obtained as aviscous yellow liquid (abbreviated hereinafter as “VAZ-PEG”).

Synthesis of methacrylated polyalkylene oxide (IEM-PEG). A mixture of2,497.79 g of poly(ethylene oxide-co-propylene oxide) (UCON-75H-90,000,Dow Chemical Co., Midland, Mich.), and a solution containing 1.23 g of2,6-di-tert-butyl-4-methylphenol (Aldrich Chemical Co., Milwaukee, Wis.)in 24.69 g. of acrylic acid (Aldrich Chemical Co., Milwaukee, Wis.) wasstirred at room temperature for 30 minutes.2-Isocyanatoethylmethacrylate (59.17 g, Aldrich Chemical Co., Milwaukee,Wis.) was then added and stirring was continued for another 30 minutes,then 0.06 g of FASCAT 4224, an organotin catalyst (Atofina Chemical Co.,Philadelphia, Pa.) was added and the mixture was stirred at roomtemperature overnight. The product was obtained as a viscous yellowliquid (abbreviated hereinafter as “IEM-PEG”).

Synthesis of methacrylated urethane polyalkylene oxide (IPH1-PEG). Amixture of 606 g of poly(ethylene oxide-co-propylene oxide)(UCON-75H-90,000, Dow Chemical Co., Midland, Mich.) and a solution of0.30 g of 2,6-di-tert-butyl-4-methylphenol (Aldrich Chemical Co.,Milwaukee, Wis.) in 3.03 g of acrylic acid (Aldrich Chemical Co.,Milwaukee, Wis.) was stirred under nitrogen for 30 minutes at roomtemperature. To this mixture 21.6 g of isophorone diisocyanate (AldrichChemical Co., Milwaukee, Wis.) and 0.021 g of FASCAT 4224, an organo tincatalyst (Atofina Chemical Co., Philadelphia, Pa.) were added and themixture was heated to 65° C. with stirring. After 6 hours, 13.41 g of2-hydroxyethyl methacrylate (Mitsubishi Rayon Co., Ltd., Tokyo, Japan)was added and heating and stirring were continued 17 hours. The productwas obtained as a yellow liquid (abbreviated hereinafter as “IPH1-PEG”).

Synthesis of methacrylated urethane polyalkylene oxide (IPH2-PEG). Amixture of 110.0 g of poly(ethylene oxide-co-propylene oxide) (UCON75-H-1400, Dow Chemical Co., Midland, Mich., number average molecular byGPC of 2,265, and weight average molecular weigh by GPC of 2,378), 12.1g of isophorone diisocyanate (Aldrich Chemical Co., Milwaukee, Wis.),65.8 g of acetone (Aldrich Chemical Co., Milwaukee, Wis.), and 5.050 gof FASCAT 4224, an organotin catalyst (Atofina Chemical Co.,Philadelphia, Pa.), was stirred under nitrogen at 55° C. After 4 hours,2.35 g of 2-hydroxyethyl methacrylate (HEMA; Mitsubishi Rayon Co., Ltd.,Tokyo, Japan), 0.050 g of 2,6-di-tert-butyl-4-methylphenol (AldrichChemical Co., Milwaukee, Wis.), and 0.62 g of acrylic acid (AldrichChemical Co., Milwaukee, Wis.) were added. After 2.5 hours at 40° C. thesolution was placed under reduced pressure to remove the acetone. Theproduct was obtained as a light yellow solution (abbreviated hereinafteras “IPH2-PEG”).

Synthesis of methacrylated urethane polyalkylene oxide (IPH3-PEG). Amixture of 199.18 g of poly(ethylene oxide-co-propylene oxide) (UCON75-H-450, Dow Chemical Co., Midland, Mich.), 52.1 g of isophoronediisocyanate (Aldrich Chemical Co., Milwaukee, Wis.), 135.3 g of acetone(Aldrich Chemical Co., Milwaukee, Wis.), and 0.094 g of FASCAT 4224, anorganotin catalyst (Atofina Chemical Co., Philadelphia, Pa.) was stirredunder nitrogen at 55° C. After 24 hours, 4.72 g of 2-hydroxyethylmethacrylate (Mitsubishi Rayon Co., Ltd., Tokyo, Japan), 0.050 g of2,6-di-tert-butyl-4-methylphenol (Aldrich Chemical Co., Milwaukee,Wis.), and 1.28 g of acrylic acid (Aldrich Chemical Co., Milwaukee,Wis.) were added. After 2.5 hours at 40° C. the solution was placedunder reduced pressure to remove the acetone. The product was obtainedas a light yellow solution (abbreviated hereinafter as “IPH3-PEG”).

Synthesis of methacrylated urethane polyalkylene oxide (TDI-PEG). Amixture of 100.0 g of poly(ethylene oxide-co-propylene oxide) (UCON75-H-1400, Dow Chemical Co., Midland, Mich.), and 8.85 g of tolylene2,4-diisocyanate (Aldrich Chemical Co., Milwaukee, Wis.) was stirredunder nitrogen at 10° C. and 0.02 g of dibutyltin dilaurate (AldrichChemical Co., Milwaukee, Wis.) was added. The mixture warmed to 40° C.After 3 hours at 40° C., 1.24 g of 2-hydroxyethyl methacrylate(Mitsubishi Rayon Co., Ltd., Tokyo, Japan) was added and stirring wascontinued for one hour. The product was obtained as a thick yellowliquid (abbreviated hereinafter as “TDI-PEG”).

Preparation of photoinitiator-IPDI (PIA-IPDI). To a continuously stirredsolution of isophorone diisocyanate (IPDI, 5.0 g, Aldrich Chemical Co.,Milwaukee, Wis.) in 50 ml CH₂Cl₂ under N₂ atmosphere was added,dropwise, a solution of IRGACURE 2959 (5 g, Ciba Specialty ChemicalCorp., Tarrytown, N.Y.) and 50 mg of dibutyltin dilaurate (AldrichChemical Co., Milwaukee, Wis.) in 50 ml CH₂Cl₂. The progress of thereaction was monitored by thin layer chromatography, TLC (CHCl₃:CH₃OH,9:1), which indicated reaction completion in 45 minutes. Solvent wasremoved in a rotary evaporator and the residue was washed several timeswith petroleum ether (Aldrich Chemical Co., Milwaukee, Wis.) until clearpetroleum ether was obtained after washings. The resulting paste wasdried in a rotary evaporator then in a vacuum pump for 6 hours at 35° C.to give colorless crystals. The structure of the product was confirmedby NMR analysis.

Preparation of photoinitiator containing polyalkylene oxide(PIA-IPDI-PEG). Polyalkyelene oxide (100 g, UCON-75H-90,000, DowChemical Co., Midland, Mich.) was dried by heating at 100° C. for 3hours with continuous stirring and N₂ stream blowing through thereactor. The viscous liquid was cooled to room temperature by turningoff the heat. To the viscous liquid was added PIA-IPDI (7.31 g) followedby a few drops (5-7) of dibutyltin dilaurate catalyst (Aldrich ChemicalCo., Milwaukee, Wis.). Stirring at room temperature was continuedovernight to give a clear liquid in quantitative yield.

Molecular Weight of Macromonomers

Molecular weight of the macromonomers was measured using Gel PermeationChromatography (GPC). Samples were prepared by the addition of 10milliliters (ml) of tetrahydrofuran (THF) to approximately 25 milligrams(mg) of sample. The solution was filtered using a 0.2-micron PTFEsyringe filter. One hundred fifty microliters of solution was injectedinto a six column set (Jordi Associates mixed bed and 500 A columns,Jordi Associates Inc., Bellingham, Mass.) in combination with a Waters2690 Separation Module (Waters Corp., Milford, Mass.), which wasoperated at room temperature, using THF as the eluent, flowing at a rateof 1.0 ml/min. Changes in concentration were detected by a HP 1047 Arefractive index detector (Hewlett Packard Instruments, Palo Alto,Calif.). The molecular weight calculations were based upon a calibrationmade of narrow dispersity polystyrenes ranging in molecular weight from6.30×10⁶ to 266. The actual calculations were completed with CALIBERsoftware (Polymer Laboratories, Inc., Amherst, Mass.) and the numbersreported are weight average molecular weights in Table 1. TABLE 1Molecular Weight of Macromonomers Macromer Mw VAZ-PEG 13,461 IBM-PEG15,191 IPH1-PEG 27,201 IPH2-PEG 18,742 IPH3-PEG 34,206 TDI-PEG20,000^(a) MAA-PEG 20,216^(a)The TDI-PEG molecular weight was determined by NMR.Saline Uptake

A jar was filled with 200 ml of 0.9% NaCl aqueous solution (saline). A3-cm diameter disk of absorbent polymer with 1.1-mm thickness of polymerwas weighed and recorded as “dry weight.” The sample was completelysubmerged in the 0.9% saline and remained submerged for 24 hours at roomtemperature. The sample was removed, allowed to drip for 1 minute, andweighed and recorded as “wet weight.” The percent uptake was calculatedusing the following formula:100×(Wet weight−dry weight)/dry weight=saline uptakeTensile Test

Tensile and elongation were measured using the following procedure. A1.1 mm thick sample of polymer was cut into a dogbone shapeapproximately 75 mm long, 9 mm wide in the center, and 13 mm wide at thethe ends. The sample was clamped perpendicular to the upper and lowerjaws of a Thwing-Albert tensile tester. The sample is then stretched ata rate of 10 inches per minute (25.4 cm/min) until it breaks. Thetensile strength is the maximum force applied to the sample at the pointof break and is reported in grams per sample width. The elongation isthe maximum percent stretch reached by the sample at the point of break.

EXAMPLES 1-3 Preparation of Absorbent Films Example 1

A mixture of 99.8 g of the macromonomer MAA-PEG and 0.20 g. of IRGACURE2959 photoinitiator (Ciba Specialty Chemical Corp., Tarrytown, N.Y.)were mixed on a roller for 24 hours then cured between two polyesterrelease liners under UV light at a total dose of 2100 mJ/cm². Theresulting polymer film was 1.1 mm thick when removed from the polyesterrelease liners.

Example 2

Example 2 was prepared as in Example 1 with macromonomer VAZ-PEG usedinstead of MAA-PEG.

Example 3

Example 3 was prepared as in Example 1 with macromonomer IEM-PEG usedinstead of MAA-PEG.

The resulting polymeric films were tested for swelling in saline. Theresults for saline uptake are in Table 2. The samples remainedtransparent after swelling. TABLE 2 IRGACURE Saline MAA-PEG VAZ-PEGIEM-PEG 2959 Uptake Example (g) (g) (g) (g) (%) 1 99.8 0 0 0.20 746 2 099.8 0 0.20 740 3 0 0 99.8 0.20 680IRGACURE 2959 from Ciba Specialty Chemical Corp., Tarrytown, NY

EXAMPLES 4-13 Preparation of Absorbent Films

Absorbent films were prepared as in Example 1 except the componentslisted in Table 3 below were used. These included a mixture of monomersas well as macromonomer and initiator. After swelling in saline, theresulting polymers remained transparent.

EXAMPLES 14-23 Preparation of Absorbent Films

Absorbent films were prepared as in Examples 1 except the mixturesincluded macromonomer IEM-PEG and the monomers and initiator listed inTable 4 below. After swelling in saline, the resulting polymers remainedtransparent.

EXAMPLES 24-31 Preparation of Absorbent Films

Absorbent films were prepared as in Example 1 except the componentslisted in Table 5 below were used. After swelling in saline, theresulting polymers remained transparent. TABLE 3 Lauryl IRGACURE α-MAA-PEG MPEG-400 Acrylate 2959 Methylstyrene Saline Uptake TensileElongation Example (g) (g) (g) (g) (g) (%) (g) (%) 4 30.2 70.0 0 0.150.14 525 469 178 5 10.0 70.4 19.8 0.14 0.17 273 192 124 6 10.1 89.8 00.15 0.15 580 166 142 7 20.2 70.0 10.0 0.16 0.23 378 298 174 8 20.8 80.10 0.18 0.15 552 474 209 9 10.3 80.0 10.2 0.15 0.17 392 176 199 10 16.776.7 6.7 0.17 0.16 429 302 163 11 13.8 77.1 6.7 0.15 0.16 433 209 127 1225.5 70.1 5.3 0.15 0.18 412 484 100 13 20.0 73.8 6.0 0.08 0.15 500 23674IRGACURE 2959 from Ciba Specialty Chemical Corp., Tarrytown, NYMethoxypolyethylene oxide 400 acrylate(MPEG 400) from Osaka OrganicChemical Industry, Ltd., Osaka, JapanLauryl acrylate and α-methylstyrene from Aldrich Chemical Co.,Milwaukee, WI

TABLE 4 IEM-PEG MPEG 400 Lauryl Acrylate IRGACURE 2959 α-MethylstyreneTensile Elongation Example (g) (g) (g) (g) (g) (g) (%) 14 30.0 69.7 00.15 0.17 116 107 15 9.9 69.8 19.2 0.15 0.17 78 146 16 10.0 89.2 0 0.140.16 70 102 17 20.0 70.0 10.3 0.14 0.14 120 171 18 20.0 80.3 0 0.14 0.1598 115 19 10.4 80.2 10.5 0.15 0.15 63 101 20 16.7 72.5 6.7 0.14 0.14 101132 21 13.8 77.0 6.5 0.14 0.15 76 123 22 25.0 72.2 5.0 0.14 0.14 126 16223 20.0 74.1 6.3 0.14 0.15 113 151IRGACURE 2959 from Ciba Specialty Chemical Corp., Tarrytown, NYMethoxypolyethylene oxide 400 acrylate (MPEG 400) from Osaka OrganicChemical Industry, Ltd., Osaka, JapanLauryl acrylate and α-methylstyrene from Aldrich Chemical Co.,Milwaukee, WI

TABLE 5 MAA-PEG MPEG 400 HEMA IRGACURE 2959 Saline Uptake TensileElongation Example (g) (g) (g) (g) (%) (g) (%) 24 20 59.8 20 0.20 427502 198 25 25 59.8 15 0.20 433 389 102 26 25 64.8 10 0.20 455 415 137 2730 59.8 10 0.20 430 521 143 28 20 64.8 15 0.20 478 304 116 29 20 69.8 100.20 497 297 108 30 15 64.8 20 0.20 512 285 124 31 15 69.8 15 0.20 527279 125IRGACURE 2959 from Ciba Specialty Chemical Corp., Tarrytown, NYMethoxypolyethylene oxide 400 acrylate (MPEG 400) from Osaka OrganicChemical Industry, Ltd., Osaka, Japan2-hydroxyethyl methacrylate (HEMA); Mitsubishi Rayon Co., Ltd., Tokyo,Japan

EXAMPLE 32

To 100 g of macromonomer MAA-PEG was added, 0.15 g of2,2′-azobis(2,4-dimethylvaleronitrile) (VAZO-52, available from duPont)and 0.1 g of 2,2′-azobis(2-methylpropionate) (available from WakoChemicals, Osaka, Japan). The mixture was knife coated at a thickness of1.1 mm thick between two 0.091 mm thick PET liners and heated at 80° C.for 30 minutes.

EXAMPLE 33

Example 33 was prepared as in Example 32 with macromonomer IEM-PEG usedinstead of MAA-PEG.

The resulting polymeric films of Examples 32 and 33 were tested forswelling in saline. The results of saline uptake are in Table 6. Thesamples remained transparent after swelling. TABLE 6 MAA-PEG IEM-PEGSaline Uptake Example (g) (g) (%) 32 100 — 308 33 — 100 644

EXAMPLE 34

A curable composition containing 36.56 parts by weight of MAA-PEG,poly(ethylene oxide-ran-propylene oxide) dimethacrylate (reactionproduct of UCON 75-H-90,000 (Dow Chemical Company, Midland, Mich.) withmethacrylic anhydride), 38.47 parts by weight of 2-hydroxyethylmethacrylate (Mistubishi Rayon Co., Tokyo, Japan), 119.52 parts byweight of methoxypolyethylene oxide 400 acrylate (Osaka Organic ChemicalCo., Osaka, Japan), 0.1 part by weight of alpha-methylstryene (AldrichChemical Co., Milwaukee, Wis.), 0.30 part by weight of IRGACURE 2959(Ciba Specialty Chemicals Corp., Tarrytown, N.Y.) and 0.09 part byweight of IRGACURE 819 (Ciba Specialty Chemicals Corp., Tarrytown, N.Y.)was cured under UV lights (2800 mJ/cm²) to give a clear, compliant filmthat was 1.1 mm thick. This film was tested for absorbency in 0.9%Saline and light transmission of hydrated samples. Transmittance andhaze were measured on Example 34 before and after gamma irradiation(23-35 kGy) using a BYK-Gardner Hazeguard Plus, a sample of hydratedDUODERM SIGNAL (ConvaTec Ltd., division of Bristol-Myers Squibb,Princeton, N.J.) was measured as a comparative and the data is presentedin Table 7. TABLE 7 Saline Absorbency Transmittance Haze Example (%) (%)(%) Example 34-before 596 97.5 1.77 gamma irradiation Example 34-after523 97.5 1.77 gamma irradiation DUODERM SIGNAL — 62.4 102.0(Comparative)

The complete disclosures of the patents, patent documents, andpublications cited herein are incorporated by reference in theirentirety as if each were individually incorporated. Variousmodifications and alterations to this invention will become apparent tothose skilled in the art without departing from the scope and spirit ofthis invention. It should be understood that this invention is notintended to be unduly limited by the illustrative embodiments andexamples set forth herein and that such examples and embodiments arepresented by way of example only with the scope of the inventionintended to be limited only by the claims set forth herein as follows.

1. A medical article comprising a gel material comprising: a homopolymeror copolymer of a multifunctional poly(alkylene oxide) free-radicallypolymerizable macromonomer having a weight average molecular weight ofat least about 2000, wherein the multifunctional poly(alkylene oxide)macromonomer comprises a copolymeric random alkylene oxide moiety of theformula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)— wherein the mole ratio ofm:n is within a range of about 1:9 to about 9:1; and R¹ is a(C1-C4)alkyl group.
 2. The medical article of claim 1 wherein the gelmaterial comprises a homopolymer of the multifunctional poly(alkyleneoxide) macromonomer.
 3. The medical article of claim 1 wherein themultifunctional macromonomer is a difunctional macromonomer of theformula:XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Y wherein: the moleratio of m:n is within a range of about 1:9 to about 9:1; and R¹ is a(C1-C4)alkyl group; and X and Y are each independently selected from thegroup consisting of

wherein R² is H or CH₃, R³ is an aromatic group, aliphatic group,alicylic group, or combinations thereof, W is an alkylene or alkyleneoxide group, and r=2-10.
 4. The medical article of claim 1 wherein thegel material comprises a copolymer of the multifunctional poly(alkyleneoxide) macromonomer.
 5. The medical article of claim 4 wherein themultifunctional macromonomer is a difunctional macromonomer of theformula:XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Y wherein: the moleratio of m:n is within a range of about 1:9 to about 9:1; and R¹ is a(C1-C4)alkyl group; and X and Y are each independently selected from thegroup consisting of

wherein R² is H or CH₃, R³ is an aromatic group, aliphatic group,alicylic group, or combinations thereof, W is an alkylene or alkyleneoxide group, and r=2-10.
 6. The medical article of claim 5 wherein R¹ ismethyl, the mole ratio of m:n is about 1:3, and X and Y are eachindependently

wherein R² is CH₃.
 7. The medical article of claim 5 wherein the gelmaterial comprises a copolymer of the multifunctional poly(alkyleneoxide) macromonomer and a monofunctional poly(alkylene oxide) monomer.8. The medical article of claim 5 wherein the gel material comprises acopolymer of the multifunctional poly(alkylene oxide) macromonomer and apolar monomer.
 9. The medical article of claim 5 comprising a copolymerof the multifunctional macromonomer, a polar monomer, a monofunctionalpoly(alkylene oxide) monomer, and a hydrophobic monomer.
 10. The medicalarticle of claim 1 wherein the multifunctional macromonomer isdifunctional.
 11. The medical article of claim 10 wherein themultifunctional macromonomer is linear.
 12. A medical article comprisinga gel material comprising a homopolymer or copolymer prepared frommonomers comprising: about 5 wt-% to 100 wt-% of a multifunctionalpoly(alkylene oxide) free-radically polymerizable macromonomer having aweight average molecular weight of at least about 2000, wherein themultifunctional poly(alkylene oxide) macromonomer comprises acopolymeric alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)— wherein the mole ratio ofm:n is within a range of about 1:9 to about 9:1; and R¹ is a(C1-C4)alkyl group; 0 wt-% to about 80 wt-% of a monofunctionalpoly(alkylene oxide) monomer; and 0 wt-% to about 40 wt-% of a polarmonomer.
 13. The medical article of claim 12 which is a wound dressingor wound packing.
 14. The medical article of claim 12 wherein the gelmaterial is transparent and absorbent.
 15. A multifunctionalmacromonomer comprising a copolymeric random alkylene oxide moiety ofthe formula:XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Y wherein the mole ratioof m:n is within a range of about 1:9 to about 9:1, R¹ is a (C1-C4)alkylgroup, and X and Y are independently selected from the group consistingof

wherein R² is H or CH₃, R³ is an aromatic group, aliphatic group,alicylic group, or combinations thereof, and W is an alkylene oralkylene oxide group.
 16. A multifunctional macromonomer comprising acopolymeric random alkylene oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)— wherein the mole ratio ofm:n is within a range of about 1:9 to about 9:1 and R¹ is a (C1-C4)alkylgroup; and wherein the macromonomer comprises two or more end groupsselected from the group consisting of

and mixtures thereof, wherein R² is H or CH₃, R³ is an aromatic group,aliphatic group, alicylic group, or combinations thereof, and W is analkylene or alkylene oxide group.
 17. A multifunctional macromonomerhaving a molecular weight of at least about 2000, wherein themultifunctional macromonomer comprises a copolymeric random alkyleneoxide moiety of the formula:XO—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)—Y wherein the mole ratioof m:n is within a range of about 1:9 to about 9:1, R¹ is a (C1-C4)alkylgroup, and X and Y are independently selected from the group consistingof

wherein R² is H or Me and r=2-10.
 18. A multifunctional macromonomerhaving a molecular weight of at least about 2000, wherein themultifunctional macromonomer comprises a copolymeric random alkyleneoxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)— wherein the mole ratio ofm:n is within a range of about 1:9 to about 9:1 and R¹ is a (C₁-C₄)alkylgroup; and wherein the macromonomer comprises two or more end groupsselected from the group consisting of

and mixtures thereof, wherein R² is H or Me and r=2-10.
 19. A polymerprepared from the macromonomer of claim
 15. 20. A polymer prepared fromthe macromonomer of claim
 16. 21. A polymer prepared from themacromonomer of claim
 17. 22. A polymer prepared from the macromonomerof claim
 18. 23. A syrup polymer mixture comprising a partiallypolymerized homopolymer or copolymer prepared from monomers comprising:about 0.1 wt-% to 100 wt-% of a multifunctional poly(alkylene oxide)free-radically polymerizable macromonomer having a weight averagemolecular weight of at least about 2000, wherein the multifunctionalpoly(alkylene oxide) macromonomer comprises a copolymeric alkylenerandom oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)— wherein the mole ratio ofm:n is within a range of about 1:9 to about 9:1; and R¹ is a(C1-C4)alkyl group; 0 wt-% to about 80 wt-% of a monofunctionalpoly(alkylene oxide) monomer; 0 wt-% to about 40 wt-% of a polarmonomer; and 0 wt-% to about 20 wt-% of a hydrophobic monomer.
 24. Amethod of making a gel, the method comprising forming a syrup polymermixture comprising a partially polymerized homopolymer or copolymerprepared from monomers comprising: about 0.1 wt-% to 100 wt-% of amultifunctional poly(alkylene oxide) free-radically polymerizablemacromonomer having a weight average molecular weight of at least about2000, wherein the multifunctional poly(alkylene oxide) macromonomercomprises a copolymeric alkylene random oxide moiety of the formula:—(—CH(R¹)—CH₂—O—)_(m) . . . (—CH₂—CH₂—O—)_(n)— wherein the mole ratio ofm:n is within a range of about 1:9 to about 9:1; and R¹ is a(C1-C4)alkyl group; 0 wt-% to about 80 wt-% of a monofunctionalpoly(alkylene oxide) monomer; 0 wt-% to about 40 wt-% of a polarmonomer; and 0 wt-% to about 20 wt-% of a hydrophobic monomer; andforming a gel from the syrup polymer mixture.
 25. The method of claim 24wherein the syrup polymer mixture comprises a photo initiator.
 26. Themethod of claim 25 wherein the step of forming a gel from the syruppolymer mixture comprises applying radiation.
 27. The method of claim 24wherein the step of forming a gel from the syrup polymer mixturecomprises applying thermal energy.
 28. The method of claim 25 whereinthe step of forming a gel from the syrup polymer mixture comprisesapplying ultraviolet radiation and thermal energy sequentially.